Purpose :
Retinal vessels are known to be affected by hypertensive retinopathy, which has been shown to be a surrogate marker for increased stroke risk. There are several software packages available to assist in retinal vessel measurements, each with its own algorithms and approach. Here we investigated the inter-rater and the inter-algorithm repeatability two commonly used free software packages, Interactive Vessel Analyzer (IVAN) and Vascular Assessment and Measurement Platform for Images of the Retina (VAMPIRE).

Methods :
Subjects were recruited from the ophthalmology clinic at the University of Minnesota. For each subject, both eyes had 50 degree color fundus photographs obtained with a Topcon fundus camera. Each image was analyzed independently by two graders, each of whom used both IVAN v1.3 (courtesy of Dr. Nicola Ferrier at the University of Wisconsin, Madison) and VAMPIRE (available at vampire.computing.dundee.ac.uk). Both were used to calculate central retinal artery equivalent (CRAE), central retinal vein equivalent (CRVE), and arteriolar:venular ratio (AVR) for each eye.

Results :
A total of 31 patients (62 eyes) were imaged; of these, 5 eyes had images that were not usable. There were 19 men and 21 women, and the average age was 76. Values for CRAE, CRVE, and AVR were plotted and a correlation coefficient between the IVAN and VAMPIRE values was calculated and tested for significance using the Pearson Product-Moment Significance Test. A two-tailed Student t-test was also performed (Table 1). The values obtained by the two algorithms correlated significantly. Likewise, inter-rater data was analyzed for each algorithm using the correlation coefficient for CRAE, CRVE, and AVR obtained by each of the two graders. The inter-rater correlation coefficient was higher for IVAN than for VAMPIRE but a Student t-test between the values did not show a significant difference (Table 1).

Conclusions :
Inter-grader CRAE, CRVE, and AVR values measured with both VAMPIRE and IVAN software packages correlated significantly, despite the differences between their algorithms. This suggests that both programs can be valuable tools in the investigation of hypertensive retinopathy and other retinal vascular conditions for which CRAE, CRVE, and AVR are relevant. However, our results showed a higher inter-grader correlation coefficient for IVAN than VAMPIRE.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.